1. Field of the Invention
The present invention relates to acoustic transducers and beamformers that form simultaneous multiple beams in multiple planes.
2. Description of the Related Technology
Devices such as Acoustic Doppler Velocity Sensors (ADVS) are widely used for measurement of vertical profiles of water current measurements and for earth and/or water referenced velocity measurement for vessel navigation. Acoustic Doppler Current Profilers (ADCP) are used in freshwater environments such as rivers, lakes and estuaries, as well as in saltwater environments such as the ocean, for studying the effects of current velocities. The measurement of accurate current velocities is important in such diverse fields as weather prediction, biological studies of nutrients, environmental studies of sewage dispersion, and commercial exploration for natural resources, including oil.
Such devices measure 3-axis velocities by measuring velocity along lines of position defined by narrow acoustic beams. Three or more beams oriented at different directions may be used to measure the three orthogonal velocity components. Such devices may employ four narrow (e.g., 1° to 4°) conical transmit/receive beams are employed positioned in two axes of a plane surface and inclined relative to the normal to that plane. In this configuration, which is referred to as a Janus configuration, two sets of narrow conical beams are symmetrically inclined outward and positioned at four 90° circumferential increments on the surface of a larger (typically 60°) outward opening cone. Marine instrumentation is frequently used in environments that are sensitive to one or more of size, power consumption, and cost. Accordingly, a need exists for suitable methods and apparatuses for generating acoustic beams for use in ADVS and ADCP devices.